Stroboscopic x-ray tube



July 4, 1967 H. FRIEDMAN 3,329,847

STROBOSCOPIC XRAY TUBE Filed July 22, 1964 INVENTOR HERBERT FRIEDMAN ATTORNEY United States Patent 3,329,847 STROBOSCOPIC X-RAY TUBE Herbert Friedman, Arlington, Va., assiguor to the United States of America as represented by the Secretary of the Navy Filed July 22, 1964, Ser. No. 384,557 10 Claims. (Cl. 313-60) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes wihout the payment of any royalties thereon or therefor.

The present invention is directed to an anode for a rotating anode type X-ray tube and more specifically to an anode that produces a pulse beam of a desired pulse shape.

Heretofore X-ray tubes have been provided which have rotating anodes in combination with a stationary electron beam incident on the anode as the anode rotates. Stationary anodes on which an electron beam is controllably moved around on the anode to produce an X-ray beam have also been used. The prior art anode structures are made of a specific metal backing with metallic inserts or plates thereon upon which an electron beam is incident. The metallic backing dissipates the heat generated whereas the metallic inserts are of a metal which produces desired X-rays. Rotating anode X-ray tubes are of various types, some make use of a rotating anode on the inside of the tube with rotating filters on the outside of the tube, others have a rotating anode in combination with a rotating sectored wheel or filters within the tube envelope to change the frequency of the X-radiation output. These tubes all have various problems in obtaining a desired pulsed X-radi-ation output. Other types make use of an alternating current to obtain pulses of X-rays with a stationary anode.

The present invention overcomes various problems by providing a rotating anode which produces a satisfactory pulsating X-ray output without the use of additional structure of external or internal filters.

It is therefore an object of the present invention to provide a suitable anode for achieving pulsating X-ray flashes.

Another object is to provide a suitable anode structure which does not require additional cooperating structure to produce pulses of X-radiation.

Another object is to provide an anode which is of simple structure and effective in producing pulses of X-radiation of the same pulse shape or of a desired different pulse shape.

Other objects, advantages and inherent function of the invention will become apparent as the same is more fully understood from the following description taken in view of the accompanying drawing which illustrates preferred embodiments, wherein:

FIG. 1 illustrates a rotating anode with an electron beam incident thereon and with X-rays emitted from the anode onto a target through a suitable window,

FIG. 2 illustrates an anode surface made in accordance to the teaching of this invention,

FIG. 3 is a cross sectional view of FIG. 2, and

FIGS. 4 and 5 illustrate modifications of the anode structure.

The present invention is directed to a rotating type anode in which the anode is so constructed to produce pulsating X-ray flashes when used in a rotating anode type X-ray tube. The anode includes a metal target area bombarded by electrons that produce the desired X-radiation. The anode has equally spaced cavities or metal inserts therein or protrusions extending therefrom formed along a circle of'the same radius in which the electron beam is focused. When the electron beam is incident on Patented July 4, 1967 the desired surface of the rotating anode, X-rays are excited therefrom in the normal manner and directed from the anode through a window in the X-ray tube envelope onto the subject matter to be X-rayed. When the electron beam is in the area of a cavity in a cavity type anode, excited X-rays cannot be seen through the window, therefore, there is no useful X-radiation emerging through the window from the area of the cavity. Thus the shape of the emerging X-radiation beam can be shaped by shaping the cavities within the surface of the anode. When the anode has metal inserts therein or protrusions extending therefrom, desired X-radiation is generated only when the electron beam is incident on the insert or the pro- 'trusion.

Now referring to the drawings, there is shown by illustration suitable structure for a rotating anode of an X-ray tube to produce a pulsating output X-ray beam in accordance to the present invention. Any conventional X-ray tube 6 that has means for rotating the anode within the envelope may be used for the purpose of this invention so long as the exit window 7 is so situated that desired X-radiation passes therethrough and the undesired radiation is blocked from emergence through the window. All of the conventional structure of any well known rotating anode X-ray tube including an electron gun 8 may be used with exception of the anode structure 9 which must be made in accordance to structure set forth therein.

The rotating anode structure, shown by illustration in FIGS. 2 and 3, is made of a light metal, disk 11 of copper, aluminum, beryllium or any other metal of good heat conductivity for dissipating the heat generated by incident electrons on the anode surface. The X-ray production area is made in the form of a circle of target metal 12 selected from a group consisting of tantalum,

tungsten, gold, molybdenum, copper, cobalt, and iron and embedded in a circular cavity 13 in the base metal such that the target metal is level or even with the base metal surface. The target metal area is provided with evenly spaced cavities 14 therein which are deep enough to prevent any X-rays generated within the cavity from emerging through the exit window, thus forming a pulsed X-ray. If desired, the cavities may be shaped such that some X-rays generated in the cavity may emerge through the exit window; therefore, the shape of the X-ray pulse may be shaped by shaping the surface upon which the electron beam that generates the X-rays are incident.

The operation for X-ray generation is the same as for conventional rotating anode X-ray generating tubes. A high velocity electron beam is incident on the heavy metal target surface of the rotating anode, generating X-radiation which emerges from the tube through an exit window. X-radiation is generated along the entire circular heavy metal target area, only when the electrons strike the cavity areas, the X-radiation cannot be directed toward the window. Only with specially shaped cavities can the X-rays emerge from the cavities and exit through the wind-ow. The frequency of the pulses can be varied by adjusting the speed of the rotating anode as well as by use of more or less numbers of cavities in the rotating anode.

A rotating anode such as shown by FIG. 4 could be made entirely of the target material 12 in which cavities 14 are made into the material on a circle about the center of the anode element. Thus X-radiation will be formed when the exciting electrons strike the target along the circle including the cavities. However, the X-radiation formed in the cavities will be blocked by the cavity wall and will not emerge through the window as described above for the anode shown by FIGS. 2 and 3.

The modification shown by illustration in FIG. 5 includes an anode base metal 11 upon which X-radiation production metal protrusions 15 are secured. X-radiation produced by electron bombardment on the metal protrusions are directed out through the window of the tube whereas any X-radiation possibly produced by the base material is blocked. The shape of the protrusions will determine the shape of the X-radiation pulse.

Thus satisfactory rotating anode X-ray tubes can be made to produce X-radiation pulses of different shapes without the use of rotating or stationary filters within or outside of the envelope.

Under some circumstances it is desired to have X-radiation pulses of different intensities and shapes such as in coding. Therefore it is possible to make the target area of different shapes or the cavities of different shapes to produce X-radiation of different pulse shapes and of different intensity.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the amended claims the invention may be practiced otherwise than as specifically described.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. An anode structure for a rotating anode type X-ray tube in which X-rays are generated by electrons incident on the anode which comprises:

a metallic base having a front side and a back side,

said base including alternating first and second X-ray generating areas on the front side of said base arranged in a circle of equal radii about the axis of said base,

said first X-ray generating areas having approximately equal dimensions with the axial dimensions between the front face of each of said first X-ray generating areas and the back side of said target base being equal,

said second X-ray generating areas having approximately equal dimensions with the axial dimension between the front face of each of said second X-ray generating areas and the back side of said target base being equal and less than the axial dimension between the front face of said first X-ray generating areas and the back side of said target base,

wall surfaces extending outwardly from said second X-radiation generating areas to said first X-radiation generating areas,

whereby X-radiation generated by said second X-ray generating area is blocked from emergence through an exit window of said X-ray tube by said wall surfaces extending outwardly from said second X-radiation generating areas to said first X-radiation generating areas.

2. An anode structure as claimed in claim 1, wherein:

said metallic base is made of a light element metal.

3. An anode structure as claimed in claim 2, wherein:

said light element metal base is selected from a group consisting of copper, aluminum and beryllium.

4. An anode structure as claimed in claim 2, wherein:

said first X-ray generating area is selected from a group consisting of tantalum, tungsten, gold, molybdenum, copper, iron and cobalt.

5. An anode structure as claimed in claim 3, wherein:

said first X-ray generating area is selected from a group consisting of tantalum, tungsten, gold, molybdenum, copper, iron, and cobalt.

6. An anode structure as claimed in claim 3, wherein:

said light element metal base is of copper.

7. An anode structure as claimed in claim 4, wherein:

said first X-ray generating area is of copper.

8. An anode structure as claimed in claim 1, in which:

said second X-ray generating areas are formed by the bottom surface of a cavity between each of said first X-ray generating areas.

9. An anode structure as claimed in claim 8, in which:

said first and second X-ray generating areas vary in their dimension across their front face.

10. An anode structure as claimed in claim 1, in which:

said first X-ray generating surfaces are formed by a plurality of spaced metal protrusions arranged in a circle on said anode element.

References Cited UNITED STATES PATENTS 1,310,714 7/1919 Rider 313-60 X 3,149,257 9/ 1964 Wintermute 31360 FOREIGN PATENTS 221,667 6/ 1962 Austria. 947,998 8/ 1956 Germany.

DAVID J. GALVIN, Primary Examiner. 

1. AN ANODE STRUCTURE FOR A ROTATING ANODE TYPE X-RAY TUBE IN WHICH X-RAYS ARE GENERATED BY ELECTRONS INCIDENT ON THE ANODE WHICH COMPRISES: A METALLIC BASE HAVING A FRONT SIDE AND A BACK SIDE, SAID BASE INCLUDING ALTERNATING FIRST AND SECOND X-RAY GENERATING AREAS ON THE FRONT SIDE OF SAID BASE ARRANGED IN A CIRCLE OF EQUAL RADII ABOUT THE AXIS OF SAID BASE, SAID FIRST X-RAY GENERATING AREAS HAVING APPROXIMATELY EQUAL DIMENSIONS WITH THE AXIAL DIMENSIONS BETWEEN THE FRONT FACE OF EACH OF SAID FIRST X-RAY GENERATING AREAS AND THE BACK SIDE OF SAID TARGET BASE BEING EQUAL, SAID SECOND X-RAY GENERATING AREAS HAVING APPROXIMATELY EQUAL DIMENSIONS WITH THE AXIAL DIMENSION BETWEN THE FRONT FACE OF EACH OF SAID SECOND X-RAY GENERATING AREAS AND THE BACK SIDE OF SAID TARGET BASE BEING EQUAL AND LESS THAN THE AXIAL DIMENSION BETWEEN THE FRONT FACE OF SAID FIRST X-RAY GENERATING AREAS AND THE BACK SIDE OF SAID TARGET BASE, WALL SURFACES EXTENDING OUTWARDLY FROM SAID SECOND X-RADIATION GENERATING AREAS TO SAID FIRST X-RADIATION GENERATING AREAS, WHEREBY X-RADIATION GENERATED BY SAID SECOND X-RAY GENERATING AREA IS BLOCKED FROM EMERGENCE THROUGH AN EXIT WINDOW OF SAID X-RAY TUBE BY SAID WALL SURFACES EXTENDING OUTWARDLY FROM SAID SECOND X-RADIATION GENERATING AREAS TO SAID FIRST X-RADIATION GENERATING AREAS. 